1. Field of the Invention
This invention generally relates to signal cable connectors and, more particularly, to a punch-down means of rapidly and securing terminating optical signal cables in a connector jack or plug.
2. Description of the Related Art
As noted in Wikipedia, plastic optical fiber (POF) is an optical fiber which is made out of plastic. Conventionally, poly(methyl methacrylate) (PMMA), a transparent thermoplastic (acrylic) alternative to glass, is the core material, and fluorinated polymers are the cladding material. Since the late 1990s however, much higher-performance POF based on perfluorinated polymers (mainly polyperfluorobutenylvinylether) has begun to appear in the marketplace.
In large-diameter fibers, 96% of the cross section is the core that allows the transmission of light. Similar to conventional glass fiber, POF transmits light (or data) through the core of the fiber. The core size of POF is in some cases 100 times larger than glass fiber.
POF has been called the “consumer” optical fiber because the fiber and associated optical links, connectors, and installation are all inexpensive. The conventional PMMA fibers are commonly used for low-speed, short-distance (up to 100 meters) applications in digital home appliances, home networks, industrial networks (PROFIBUS, PROFINET), and car networks (MOST). The perfluorinated polymer fibers are commonly used for much higher-speed applications such as data center wiring and building LAN wiring.
For telecommunications, the more difficult-to-use glass optical fiber is more common. This fiber has a core made of germania-doped silica. Although the actual cost of glass fibers is lower than plastic fiber, their installed cost is much higher due to the special handling and installation techniques required. One of the most exciting developments in polymer fibers has been the development of microstructured polymer optical fibers (mPOF), a type of photonic crystal fiber.
In summary, POF uses PMMA or polystyrene as a fiber core, with refractive indices of 1.49 & 1.59, respectively. The fiber cladding overlying the core is made of silicone resin (refractive index ˜1.46). A high refractive index difference is maintained between core and cladding. POF have a high numerical aperture, high mechanical flexibility, and low cost.
Generally, POF is terminated in cable assembly connectors using a method that trims the cables, epoxies the cable into place, and cures the epoxy. ST style connectors, for example, include a strain relief boot, crimp sleeve, and connector (with ferrule). The main body of the connector is epoxied to the fiber, and fiber is threaded through the crimp sleeve to provide mechanical support. The strain relief boot prevents to fiber from being bent in too small of a radius. Some connectors rely upon the connector shape for mechanical support, so a crimp sleeve is not necessary.
First, the strain relief boot and crimp sleeve are slid onto the cable. A jacket stripping tool must be used to remove the end portion of the fiber, exposing an aramid yarn (e.g., Kevlar™) covered buffer or cladding layer. Next, a buffer stripping tool is used to remove a section of the buffer layer, exposing the core. After mixing, a syringe is filled with epoxy. A bead of epoxy is formed at the end of the ferrule, and the ferrule back-filled with epoxy. The exposed fiber core is threaded through the connector ferrule with a rotating motion, to spread the epoxy, until the jacket meets the connector. At this point the crimping sleeve is slide onto the connector body and crimped in two places. Then, the strain relief boot can be slide over the crimp sleeve. After the epoxy cures, the core extending through the ferrule is polished with a lapping film. Then, the core is scribed at the point where it extends from the epoxy bead. The extending core potion is then cleaved from the connector and polished in multiple steps.
It would be advantageous if an optical fiber could be quickly attached to a connector.
It would be advantageous if an efficient crimping method could be used to attach an optical fiber to a connector, avoiding processes that heat the fiber, as heating processes are known to curl the fiber.